The role of CD8+CD28 regulatory cells in suppressing myasthenia gravis-associated responses by a dual altered peptide ligand

Increased levels of regulatory T cells and IL-10-producing regulatory B cells are linked to improved clinical outcome in Parkinson's disease: a 1-year observational study

Whilst the contribution of peripheral and central inflammation to neurodegeneration in Parkinson's disease and the role of the immune response in this disorder are well known, the effects of the anti-inflammatory response on the disease have not been described in depth. This study is aimed to assess the changes in the regulatory/inflammatory immune response in recently diagnosed, untreated PD patients and a year after. Twenty-one PD patients and 19 healthy controls were included and followed-up for 1 year. The levels of immunoregulatory cells (CD4+ Tregs, Bregs, and CD8+ Tregs); classical, nonclassical, and intermediate monocytes, and proinflammatory cells (Th1, Th2, and Th17) were measured by flow cytometry. Cytokine levels were determined by ELISA. Clinical follow-up was based on the Hoehn & Yahr and UDPRS scales. Our results indicate that the regulatory response in PD patients on follow-up was characterized by increased levels of active Tregs, functional Tregs, TR1, IL-10-producing functional Bregs, and IL-10-producing classical monocytes, along with decreased counts of Bregs and plasma cells. With respect to the proinflammatory immune response, peripheral levels of Th1 IFN-γ+ cells were decreased in treated PD patients, whilst the levels of CD4+ TBET+ cells, HLA-DR+ intermediate monocytes, IL-6, and IL-4 were increased after a 1-year follow-up. Our main finding was an increased regulatory T cell response after a 1-year follow-up and its link with clinical improvement in PD patients. In conclusion, after a 1-year follow-up, PD patients exhibited increased levels of regulatory populations, which correlated with clinical improvement. However, a persistent inflammatory environment and active immune response were observed.

Causal relationship between immune cells and the risk of myeloperoxidase antineutrophil cytoplasmic antibody-associated vasculitis: A Mendelian randomization study

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare inflammatory disease categorized as antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. The majority of patients are ANCA-positive, predominantly against myeloperoxidase (MPO). Previous studies have predominantly concentrated on the association between EGPA and neutrophils, but recent research has emphasized the role of lymphocytes in the development of EGPA. The objective of our research was to examine the causal association between immune cells and MPO + ANCA EGPA. A two-sample bidirectional Mendelian randomization (MR) analysis was performed, which included 159 MPO + ANCA EGPA cases and 6688 controls and utilized Genome-Wind Associaton Studies (GWAS) summary statistics of immune traits from approximately 3757 individuals, encompassing around 22 million single nucleotide polymorphisms (SNPs). Our findings revealed that 23 immunophenotypes were associated with MPO + ANCA EGPA. Furthermore, the reverse MR analysis showed that MPO + ANCA EGPA had significant causal effects on three immunophenotypes within the Treg panel. By integrating existing research, our study unveiled the contributions of Tregs, B cells, and monocytes to the development of EGPA. Subgroup analysis specifically examined the roles of lymphocyte subtypes, cytokines, and their surface molecules in the pathogenic mechanisms of the disease. This comprehensive approach provides a novel perspective on the biological mechanisms and early intervention strategies for MPO + ANCA EGPA by focusing on immune cells.

An angel or a devil? Current view on the role of CD8+ T cells in the pathogenesis of myasthenia gravis

BACKGROUND

Myasthenia gravis (MG) and the experimental autoimmune MG (EAMG) animal model are characterized by T-cell-induced and B-cell-dominated autoimmune diseases that affect the neuromuscular junction. Several subtypes of CD4+ T cells, including T helper (Th) 17 cells, follicular Th cells, and regulatory T cells (Tregs), contribute to the pathogenesis of MG. However, increasing evidence suggests that CD8+ T cells also play a critical role in the pathogenesis and treatment of MG.

MAIN BODY

Herein, we review the literature on CD8+ T cells in MG, focusing on their potential effector and regulatory roles, as well as on relevant evidence (peripheral, in situ, cerebrospinal fluid, and under different treatments), T-cell receptor usage, cytokine and chemokine expression, cell marker expression, and Treg, Tc17, CD3+CD8+CD20+ T, and CXCR5+ CD8+ T cells.

CONCLUSIONS

Further studies on CD8+ T cells in MG are necessary to determine, among others, the real pattern of the Vβ gene usage of autoantigen-specific CD8+ cells in patients with MG, real images of the physiology and function of autoantigen-specific CD8+ cells from MG/EAMG, and the subset of autoantigen-specific CD8+ cells (Tc1, Tc17, and IL-17+IFN-γ+CD8+ T cells). There are many reports of CD20-expressing T (or CD20 + T) and CXCR5+ CD8 T cells on autoimmune diseases, especially on multiple sclerosis and rheumatoid arthritis. Unfortunately, up to now, there has been no report on these T cells on MG, which might be a good direction for future studies.

CD8+ T regulatory cells in lupus

T regulatory cells (Tregs) have a key role in the maintenance of immune homeostasis and the regulation of immune tolerance by preventing the inflammation and suppressing the autoimmune responses. Numerical and functional deficits of these cells have been reported in systemic lupus erythematosus (SLE) patients and mouse models of SLE, where their imbalance and dysregulated activities have been reported to significantly influence the disease pathogenesis, progression and outcomes. Most studies in SLE have focused on CD4+ Tregs and it has become clear that a critical role in the control of immune tolerance after the breakdown of self-tolerance is provided by CD8+ Tregs. Here we review the role, cellular and molecular phenotypes, and mechanisms of action of CD8+ Tregs in SLE, including ways to induce these cells for immunotherapeutic modulation in SLE.

Pro- and anti-inflammatory response in neurological disorders associated to anti-glutamate decarboxylase antibodies

Rare conditions showing psychiatric symptoms and movement disorders have been linked with the presence of anti-glutamate decarboxylase antibodies. Proinflammatory and antiinflammatory immune responses were assessed in patients with neurological disorders associated to anti-glutamic acid decarboxylase antibodies (NDGAD). Immunoregulatory and proinflammatory cell populations were quantified by flow cytometry. No polarization toward Th1, Th2, or Th17 phenotypes was observed in NDGAD patients. Immunoregulatory responses were significantly reduced for Breg, activated Treg, Tr1, and Th3 cells, suggesting a deficient regulatory response, while intermediate monocyte levels were increased. The reduced levels of regulatory T and B cells suggest an impairment in regulatory immune response, while intermediate monocytes could be playing a role in the increased proinflammatory response.

Identification of the association of CD28+ CD244+ Tc17/IFN-γ cells with chronic hepatitis C virus infection

CD8+ T cells play multiple and complex immunological roles including antiviral, regulatory, and exhaustive effects in hepatitis C virus (HCV) infected patients. Some CD8+ T-cell subsets were confirmed to be closely related to HCV infection such as TCM , TEM , TEM RA, Tc17, and CD8+ Treg. Herein, we report a new subset of interleukin (IL)-17/interferon (IFN)-γ producing CD8+ T (Tc17/IFN-γ) cells that markedly correlate with CD28+ CD244+ cells, IL-17 levels, and HCV RNA in HCV patients. During early treatment with peg-IFN-a2a plus ribavirin, the imbalance of these Tc17/IFN-γ cells could be partially restored, together with normalized serum alanine aminotransferase but not aspartate transaminase. Also, we analyzed the dynamic change of the percentage of this T cells subset in patients with different outcome after 4-week course of treatment with peg-IFN-a2a plus ribavirin and found that the percentage of CD8+ CD28+ CD244+ T cells significantly decreased in recovered patients but not in nonrecovered patients. In vitro, CD28+ CD244+ T cells were the only CD8+ T-cell group that secreted both IL-17 and IFN-γ in this axis and blockade with anti-CD244 antibodies significantly reduced cytokine production. Taken together, this study demonstrates that the frequency and regulatory functions of CD28+ CD244+ Tc17/IFN-γ cells may play an important role in persistent HCV infection.

Regulatory impairment in untreated Parkinson's disease is not restricted to Tregs: other regulatory populations are also involved

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disease in the world. Various studies have suggested that the immune response plays a key role in this pathology. While a predominantly pro-inflammatory peripheral immune response has been reported in treated and untreated PD patients, the study of the role of the regulatory immune response has been restricted to regulatory T cells. Other immune suppressive populations have been described recently, but their role in PD is still unknown. This study was designed to analyze the pro and anti-inflammatory immune response in untreated PD patients, with emphasis on the regulatory response.

METHODS

Thirty-two PD untreated patients and 20 healthy individuals were included in this study. Peripheral regulatory cells (CD4+Tregs, Bregs, CD8+Tregs, and tolerogenic dendritic cells), pro-inflammatory cells (Th1, Th2, and Th17 cells; active dendritic cells), and classical, intermediate, and non-classical monocytes were characterized by flow cytometry. Plasmatic levels of TNF-α, IFN-γ, IL-6, GM-CSF, IL-12p70, IL-4, IL-13, IL-17α, IL-1β, IL-10, TGF-β, and IL-35 were determined by ELISA.

RESULTS

Decreased levels of suppressor Tregs, active Tregs, Tr1 cells, IL-10-producer CD8regs, and tolerogenic PD-L1+ dendritic cells were observed. With respect to the pro-inflammatory response, a decrease in IL-17-α and an increase in IL-13 levels were observed.

CONCLUSION

A decrease in the levels of regulatory cell subpopulations in untreated PD patients is reported for the first time in this work. These results suggest that PD patients may exhibit a deficient suppression of the pro-inflammatory response, which could contribute to the pathophysiology of the disease.

Cre-loxP Reporter Mouse Reveals Stochastic Activity of the Foxp3 Promoter

Mouse models that combine specific loxP-flanked gene sequences with Cre recombinase expressed from cell-regulated promoters have become important tools to investigate gene function. Critically however, expression of Cre recombinase may not always be restricted to the target cell or tissue of interest due to promiscuous activity of the driving promoter. Expression of Cre recombinase and, by extension, excision of the loxP-flanked gene may occur in non-target cells and may not be readily apparent. Here we report on the fidelity of Cre recombinase expressed from the il17a or Foxp3 promoters by combining them with a constitutively expressed floxed-stopped tdTomato reporter gene. Foxp3-driven Cre recombinase in F₁ mice induced tdTomato red fluorescent protein in Treg cells but also in a range of other immune cells. Frequency of tdTomato expression was variable but positively correlated (p < 0.0001) amongst lymphoid (B cells and CD8 T cells) and blood-resident myeloid cells (dendritic cells, monocytes, neutrophils) suggesting stochastic activity of the Foxp3 promoter rather than developmental regulation in common ancestral progenitors. Interestingly, frequency of tdTomato⁺ dendritic cells, monocytes and neutrophils did not correlate with the tdTomato⁺ fraction in eosinophils, indicating that activity of the Foxp3 promoter in eosinophils occurred after the split from a common multipotent progenitor. When these F₁ mice were crossed to achieve homozygosity of the promoter and reporter gene, a novel visually red phenotype was observed segregating amongst littermates. The red coloration was widespread and prevalent in non-immune tissues. Thymocytes examined from these red mice showed that all four subsets of immature thymocytes (CD4⁻ CD8⁻) based on differential expression of CD25 and CD44 were expressing tdTomato. Finally, we show evidence of Foxp3 Cre recombinase independent tdTomato expression, suggesting germ line transmission of an activated tdTomato reporter gene. Our data highlights potential issues with conclusions drawn from using specifically the B6.129(Cg)-Foxp3^{tm4(YFP/Cre)Ayr}/J mice.

Suppression of Murine Lupus by CD4+ and CD8+ Treg Cells Induced by T Cell-Targeted Nanoparticles Loaded With Interleukin-2 and Transforming Growth Factor β

OBJECTIVE

To develop a nanoparticle (NP) platform that can expand both CD4+ and CD8+ Treg cells in vivo for the suppression of autoimmune responses in systemic lupus erythematosus (SLE).

METHODS

Poly(lactic-co-glycolic acid) (PLGA) NPs encapsulating interleukin-2 (IL-2) and transforming growth factor β (TGFβ) were coated with anti-CD2/CD4 antibodies and administered to mice with lupus-like disease induced by the transfer of DBA/2 T cells into (C57BL/6 × DBA/2)F₁ (BDF1) mice. The peripheral frequency of Treg cells was monitored ex vivo by flow cytometry. Disease progression was assessed by measuring serum anti-double-stranded DNA antibody levels by enzyme-linked immunosorbent assay. Kidney disease was defined as the presence of proteinuria or renal histopathologic features.

RESULTS

Anti-CD2/CD4 antibody-coated, but not noncoated, NPs encapsulating IL-2 and TGFβ induced CD4+ and CD8+ FoxP3+ Treg cells in vitro. The optimal dosing regimen of NPs for expansion of CD4+ and CD8+ Treg cells was determined in in vivo studies in mice without lupus and then tested in BDF1 mice with lupus. The administration of anti-CD2/CD4 antibody-coated NPs encapsulating IL-2 and TGFβ resulted in the expansion of CD4+ and CD8+ Treg cells, a marked suppression of anti-DNA antibody production, and reduced renal disease.

CONCLUSION

This study shows for the first time that T cell-targeted PLGA NPs encapsulating IL-2 and TGFβ can expand both CD4+ and CD8+ Treg cells in vivo and suppress murine lupus. This approach, which enables the expansion of Treg cells in vivo and inhibits pathogenic immune responses in SLE, could represent a potential new therapeutic modality in autoimmune conditions characterized by impaired Treg cell function associated with IL-2 deficiency.

Restoring self-tolerance in autoimmune diseases by enhancing regulatory T-cells

Self-tolerance, the state of unresponsiveness to self-tissues/antigens, is maintained through central and peripheral tolerance mechanisms, and a breach of these mechanisms leads to autoimmune diseases. Foxp3 + T-regulatory cells (Tregs) play an essential role in suppressing autoimmune response directed against self-antigens and thereby regulate self-tolerance. Natural Tregs are differentiated in the thymus on the basis of their higher TCR-affinity to self-antigens and migrate to the periphery where they maintain peripheral tolerance. In addition, extra-thymic differentiation of induced Tregs can occur in the periphery which can control abrupt immune responses under inflammatory conditions. A defect in Treg cell numbers and/or function is found to be associated with the development of autoimmune disease in several experimental models and human autoimmune diseases. Moreover, augmentation of Tregs has been shown to be beneficial in treating autoimmunity in preclinical models, and Treg based cellular therapy has shown initial promise in clinical trials. However, emerging studies have identified an unstable subpopulation of Tregs which expresses pro-inflammatory cytokines under both homeostatic and autoimmune conditions, as well as in ex vivo cultures. In addition, clinical translation of Treg cellular therapy is impeded by limitations such as lack of easier methods for selective expansion of Tregs and higher cost associated with GMP-facilities required for cell sorting, ex vivo expansion and infusion of ex vivo expanded Tregs. Here, we discuss the recent advances in molecular mechanisms regulating Treg differentiation, Foxp3 expression and lineage stability, the role of Tregs in the prevention of various autoimmune diseases, and critically review their clinical utility for treating human autoimmune diseases.

Foxp3, Regulatory T Cell, and Autoimmune Diseases

Regulatory T cells (Tregs) represent a cell type that promotes immune tolerance to autologous components and maintains immune system homeostasis. The abnormal function of Tregs is relevant to the pathogenesis of systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and other autoimmune diseases. Therefore, therapeutic modulation of Tregs could be a potent means of treating autoimmune diseases. Human Tregs are diverse, however, and not all of them have immunosuppressive effects. Forkhead box P3 (Foxp3), a pivotal transcription factor of Tregs that is crucial in maintaining Treg immunosuppressive function, can be expressed heterogeneously or unstably across Treg subpopulations. Insights into modulating Treg differentiation on the level of DNA transcription or protein modification may improve the success of Treg modifying immunotherapies. In this review, we will summarize three main prospects: the regulatory mechanism of Foxp3, the influence on Foxp3 and Tregs in autoimmune diseases, then finally, how Tregs can be used to treat autoimmune diseases.

CD28- and CD28lowCD8+ Regulatory T Cells: Of Mice and Men

Since the rebirth of regulatory (formerly known as suppressor) T cells in the early 1990s, research in the field of immune-regulation by various T cell populations has quickly gained momentum. While T cells expressing the transcription factor Foxp3 are currently in the spotlight, several other T cell populations endowed with potent immunomodulatory capacities have been identified in both the CD8⁺ and CD4⁺ compartment. The fundamental difference between CD4⁺ and CD8⁺ T cells in terms of antigen recognition suggests non-redundant, and perhaps complementary, functions of regulatory CD4⁺ and CD8⁺ T cells in immunoregulation. This emphasizes the importance and necessity of continuous research on both subpopulations of regulatory T cells (Tregs) so as to decipher their complex physiological relevance and possible synergy. Two distinct CD8-expressing Treg populations can be distinguished based on expression of the co-stimulatory receptor CD28. Here, we review the literature on these (at least in part) thymus-derived CD28^low and peripherally induced CD28^-CD8⁺ Tregs.

On Peptides and Altered Peptide Ligands: From Origin, Mode of Action and Design to Clinical Application (Immunotherapy)

T lymphocytes equipped with clonotypic T cell antigen receptors (TCR) recognize immunogenic peptides only when presented in the context of their own major histocompatibility complex (MHC) molecules. Peptide loading to MHC molecules occurs in intracellular compartments (ER for class I and MIIC for class II molecules) and relies on the interaction of the respective peptides and peptide binding pockets on MHC molecules. Those peptide residues not engaged in MHC binding point towards the TCR screening for possible peptide MHC complex binding partners. Natural or intentional modification of both MHC binding registers and TCR interacting residues of peptides - leading to the formation of altered peptide ligands (APLs) - might alter the way peptides interact with TCRs and hence influence subsequent T cell activation events, and consequently T cell effector functions. This review article summarizes how APLs were detected and first described, current concepts of how APLs modify T cellular signaling, which biological mechanisms might force the generation of APLs in vivo, and how peptides and APLs might be used for the benefit of patients suffering from allergic or autoimmune diseases.

Gene expression profiling of CD8+ T cells induced by ovarian cancer cells suggests a possible mechanism for CD8+ Treg cell production

OBJECTIVES

The aim of this study was to investigate a possible mechanism of CD8⁺ regulatory T-cell (Treg) production in an ovarian cancer (OC) microenvironment.

MATERIALS AND METHODS

Agilent microarray was used to detect changes in gene expression between CD8⁺ T cells cultured with and without the SKOV3 ovarian adenocarcinoma cell line. QRT-PCR was performed to determine glycolysis gene expression in CD8⁺ T cells from a transwell culturing system and OC patients. We also detected protein levels of glycolysis-related genes using Western blot analysis.

RESULTS

Comparing gene expression profiles revealed significant differences in expression levels of 1420 genes, of which 246 were up-regulated and 1174 were down-regulated. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis indicated that biological processes altered in CD8⁺ Treg are particularly associated with energy metabolism. CD8⁺ Treg cells induced by co-culture with SKOV3 had lower glycolysis gene expression compared to CD8⁺ T cells cultured alone. Glycolysis gene expression was also decreased in the CD8⁺ T cells of OC patients.

CONCLUSIONS

These findings provide a comprehensive bioinformatics analysis of DEGs in CD8⁺ T cells cultured with and without SKOV3 and suggests that metabolic processes may be a possible mechanism for CD8⁺ Treg induction.

Mouse and human CD8(+) CD28(low) regulatory T lymphocytes differentiate in the thymus

Regulatory T (Treg) lymphocytes play a central role in the control of immune responses and so maintain immune tolerance and homeostasis. In mice, expression of the CD8 co-receptor and low levels of the co-stimulatory molecule CD28 characterizes a Treg cell population that exerts potent suppressive function in vitro and efficiently controls experimental immunopathology in vivo. It has remained unclear if CD8(+) CD28(low) Treg cells develop in the thymus or represent a population of chronically activated conventional T cells differentiating into Treg cells in the periphery, as suggested by their CD28(low) phenotype. We demonstrate that functional CD8(+) CD28(low) Treg cells are present in the thymus and that these cells develop locally and are not recirculating from the periphery. Differentiation of CD8(+) CD28(low) Treg cells requires MHC class I expression on radioresistant but not on haematopoietic thymic stromal cells. In contrast to other Treg cells, CD8(+) CD28(low) Treg cells develop simultaneously with CD8(+) CD28(high) conventional T cells. We also identified a novel homologous naive CD8(+) CD28(low) T-cell population with immunosuppressive properties in human blood and thymus. Combined, our data demonstrate that CD8(+) CD28(low) cells can develop in the thymus of mice and suggest that the same is true in humans.

Taming the TCR: antigen-specific immunotherapeutic agents for autoimmune diseases

Current treatments for autoimmune diseases are typically non-specific anti-inflammatory agents that affect not only the autoreactive cells but also the parts of the immune system that are required to maintain health. There is a need for the development of antigen-specific therapeutic agents that can effectively prevent the autoimmune attack while leaving the rest of the immune system functioning as normal. The simplest way to achieve this is using the autoantigen itself as a tolerizing agent; however, there is some risk involved with administering a potentially pathogenic antigen. In this review, we focus instead on the development and use of modified T cell receptor (TCR) ligands, in which the peptide ligand is modified to change the response by the T cell from a disease inducing to a protective response, and still retain the antigen-specificity necessary to target the autoreactive T cells. We review the use of modified TCR ligands as therapeutic agents in animal models of autoimmunity and in human autoimmune disease, and finally consider how they need to be improved in order to use them effectively in patients with autoimmune disease.

Numerical status of CD4(+)CD25(+)FoxP3(+) and CD8(+)CD28(-) regulatory T cells in multiple sclerosis

OBJECTIVES

Regulatory T cells, including CD4+CD25+Fox3+ and CD8+CD28- cells play an important role in regulating the balance between immunity and tolerance. Since multiple sclerosis is an inflammatory autoimmune disease, regulatory T cells are considered to be involved in its pathogenesis. In this study, we investigated the circulatory numbers of the two mentioned types of regulatory T cells and also their association with different clinical characteristics in 84 multiple sclerosis patients.

MATERIALS AND METHODS

84 patients with multiple sclerosis and 75 normal individuals were studied. Demographic and clinical information of all participants were collected via questionnaire and clinical examination as well as MRI. The peripheral blood frequency of two different subgroups of regulatory T cells (CD4+ CD25+Foxp3+ and CD8+CD28- cells) were analyzed by flow cytometry using anti-human antibodies conjugated with CD4-FITC / CD25-PE/Foxp3-PE-Cy5, CD3-PE/CD8a-PE-Cy5/CD28-FITC.

RESULTS

The frequency of CD4+CD25+Foxp3+ cells in multiple sclerosis patients was significantly less than that in healthy controls (P=0.006) and in mild forms less than that in sever forms (P=0.003). There was not any correlation between the frequency of regulatory T cells and different clinical variables.

CONCLUSION

Our results showed that the number of CD4+CD25+Foxp3+ cells decreases significantly in multiple sclerosis patients, which probably shows the regulatory role of these cells in multiple sclerosis.

Promotion and prevention of autoimmune disease by CD8+ T cells

Until recently, little was known about the importance of CD8+ T effectors in promoting and preventing autoimmune disease development. CD8+ T cells can oppose or promote autoimmune disease through activities as suppressor cells and as cytotoxic effectors. Studies in several distinct autoimmune models and data from patient samples are beginning to establish the importance of CD8+ T cells in these diseases and to define the mechanisms by which these cells influence autoimmunity. CD8+ effectors can promote disease via dysregulated secretion of inflammatory cytokines, skewed differentiation profiles and inappropriate apoptosis induction of target cells, and work to block disease by eliminating self-reactive cells and self-antigen sources, or as regulatory T cells. Defining the often major contribution of CD8+ T cells to autoimmune disease and identifying the mechanisms by which they alter the pathogenesis of disease is a rapidly expanding area of study and will add valuable information to our understanding of the kinetics, pathology and biology of autoimmune disease.

CD11c(high)CD8+ regulatory T cell feedback inhibits CD4 T cell immune response via Fas ligand-Fas pathway

Regulatory T cells can restrict the uncontrolled immune response and inflammation, avoiding pathologic immune injury to the host and thus playing important roles in the maintenance of immune homeostasis. Until recently, many subsets of CD4 and CD8 regulatory T cells have been reported. In this study, we identified CD11c(high)CD8(+) T cells as a new subset of CD8(+) regulatory T cells. During Listeria monocytogenes and Staphylococcus aureus infection, two subsets of CD8 T cells were classified according to the expression level of CD11c, including CD11c(low)CD8(+) and CD11c(high)CD8(+) T cells. CD11c(low)CD8(+) T cells, existing during the whole period of infection, act as conventional activated T cells to kill target cells in a perforin-dependent manner. Interestingly, CD11c(high)CD8(+) T cells appeared only at a late stage of infection, expressed relatively high CD122 and low CD69, did not secrete IFN-γ, IL-10, TGF-β, and exhibited much more potent cytotoxicity against target cells via Fas ligand-Fas pathway in an Ag-independent manner. Ligation of CD11c was important in the cytotoxicity of CD11c(high)CD8(+) T cells. Furthermore, CD11c(high)CD8(+) T cells could directly kill the activated CD4 T cells both in vitro and in vivo, whereas CD11c(low)CD8(+) T cells could not. Thus, we identified an infection-induced new subset of CD11c(high)CD8(+) regulatory T cells, which might contribute to protect host from pathological immune injure. Our results indicate that CD11c(+)CD8(+) T cells are constitute a heterogeneous population that can be divided further into regulatory CD11c(high)CD8(+) T cell subset and effector CD11c(low)CD8(+) T cell subset, thus adding insight to the role of CD8 T cells in immune response and regulation.

Ectonucleotidase CD38 demarcates regulatory, memory-like CD8+ T cells with IFN-γ-mediated suppressor activities

Regulatory CD8(+) T cells are critical for self-tolerance and restricting excessive immune responses. The variety of immune functions they fulfill, the heterogeneity of their phenotype, and the mechanism of action are still poorly understood. Here we describe that regulatory CD8(+) T cells exhibiting immunosuppressive actions in vitro and in vivo are recognized as CD38(high) T cells and present in naive mice. CD38 is a glycosylated membrane protein with ectonucleotidase properties. CD8(+)CD38(high) (CD44(+)CD122(+)CD62L(high)) lymphocytes suppress CD4(+) effector T-cell proliferation in an antigen-non specific manner via IFN-γ. While direct cell-to-cell contact is needed for this suppressor activity, it is independent of membrane-bound TGF-β and granzyme B release. IL-15 potentiates the suppressive activity of CD8(+)CD38(high) T cells and controls their survival and expansion. In humans CD8(+)CD38(high) T cells inhibit CD4(+) effector T cell proliferation. In vivo, CD8(+)CD38(high), but not CD8(+)CD38(-) T cells mitigate murine experimental autoimmune encephalomyelitis (EAE) by reducing the clinical score and delaying disease occurrence. EAE suppression is enhanced by pre-treatment of CD8(+)CD38(high) T cells with IL-15. These findings add evidence that the expression of ectoenzyme receptor family members positively correlates with suppressor functions and identifies CD8(+)CD38(high) T cells as potential inhibitors of excessive immune responses.

Identification and expansion of highly suppressive CD8(+)FoxP3(+) regulatory T cells after experimental allogeneic bone marrow transplantation

FoxP3(+) confers suppressive properties and is confined to regulatory T cells (T(reg)) that potently inhibit autoreactive immune responses. In the transplant setting, natural CD4(+) T(reg) are critical in controlling alloreactivity and the establishment of tolerance. We now identify an important CD8(+) population of FoxP3(+) T(reg) that convert from CD8(+) conventional donor T cells after allogeneic but not syngeneic bone marrow transplantation. These CD8(+) T(reg) undergo conversion in the mesenteric lymph nodes under the influence of recipient dendritic cells and TGF-β. Importantly, this population is as important for protection from GVHD as the well-studied natural CD4(+)FoxP3(+) population and is more potent in exerting class I-restricted and antigen-specific suppression in vitro and in vivo. Critically, CD8(+)FoxP3(+) T(reg) are exquisitely sensitive to inhibition by cyclosporine but can be massively and specifically expanded in vivo to prevent GVHD by coadministering rapamycin and IL-2 antibody complexes. CD8(+)FoxP3(+) T(reg) thus represent a new regulatory population with considerable potential to preferentially subvert MHC class I-restricted T-cell responses after bone marrow transplantation.

Cell-autonomous role of TGFβ and IL-2 receptors in CD4+ and CD8+ inducible regulatory T-cell generation during GVHD

FoxP3(+) regulatory T cells (Tregs) suppress GVHD while preserving graft-versus-tumor effects, making them an attractive target for GVHD therapy. The donor-derived Treg pool can potentially be derived from the expansion of preexisting natural Tregs (nTregs) or from de novo generation of inducible Tregs (iTregs) from donor Tconvs in the transplantation recipient. Using an MHC-mismatched model of acute GVHD, in the present study we found that the Treg pool was comprised equally of donor-derived nTregs and iTregs. Experiments using various combinations of T cells from wild-type and FoxP3-deficient mice suggested that both preexisting donor nTregs and the generation of iTregs in the recipient mice contribute to protection against GVHD. Surprisingly, CD8(+)FoxP3(+) T cells represented approximately 70% of the iTreg pool. These CD8(+)FoxP3(+) T cells shared phenotypic markers with their CD4(+) counterparts and displayed suppressive activity, suggesting that they were bona fide iTregs. Both CD4(+) and CD8(+) Tregs appeared to be protective against GVHD-induced lethality and required IL-2 and TGFβ receptor expression for their generation. These data illustrate the complex makeup of the donor-derived FoxP3(+) Treg pool in allogeneic recipients and their potential role in protection against GVHD.

CD8(+) Tregs in autoimmunity: learning "self"-control from experience

Autoreactive CD8(+) regulatory T cells (Tregs) play important roles as modulators of immune responses against self, and numerical and functional defects in CD8(+) Tregs have been linked to autoimmunity. Several subsets of CD8(+) Tregs have been described. However, the origin of these T cells and how they participate in the natural progression of autoimmunity remain poorly defined. We discuss several lines of evidence suggesting that the autoimmune process itself promotes the development of autoregulatory CD8(+) T cells. We posit that chronic autoantigenic exposure fosters the differentiation of non-pathogenic autoreactive CD8(+) T cells into antigen-experienced, memory-like autoregulatory T cells, to generate a "negative feedback" regulatory loop capable of countering pathogenic autoreactive effectors. This hypothesis predicts that approaches capable of boosting autoregulatory T cell memory will be able to blunt autoimmunity without compromising systemic immunity.

Genes, tolerance and systemic autoimmunity

The characterization of functional CD8(+) inhibitory or regulatory T cells and their gene regulation remains a critical challenge in the field of tolerance and autoimmunity. Investigating the genes induced in regulatory cells and the regulatory networks and pathways that underlie mechanisms of immune resistance and prevent apoptosis in the CD8(+) T cell compartment are crucial to understanding tolerance mechanisms in systemic autoimmunity. Little is currently known about the genetic control that governs the ability of CD8(+) Ti or regulatory cells to suppress anti-DNA Ab production in B cells. Silencing genes with siRNA or shRNA and overexpression of genes with lentiviral cDNA transduction are established approaches to identifying and understanding the function of candidate genes in tolerance and immunity. Elucidation of interactions between genes and proteins, and their synergistic effects in establishing cell-cell cross talk, including receptor modulation/antagonism, are essential for delineating the roles of these cells. In this review, we will examine recent reports which describe the modulation of cells from lupus prone mice or lupus patients to confer anti-inflammatory and protective gene expression and novel associated phenotypes. We will highlight recent findings on the role of selected genes induced by peptide tolerance in CD8(+) Ti.

CD8+ CD28- and CD8+ CD57+ T cells and their role in health and disease

Chronic antigenic stimulation leads to gradual accumulation of late-differentiated, antigen-specific, oligoclonal T cells, particularly within the CD8(+) T-cell compartment. They are characterized by critically shortened telomeres, loss of CD28 and/or gain of CD57 expression and are defined as either CD8(+) CD28(-) or CD8(+) CD57(+) T lymphocytes. There is growing evidence that the CD8(+) CD28(-) (CD8(+) CD57(+)) T-cell population plays a significant role in various diseases or conditions, associated with chronic immune activation such as cancer, chronic intracellular infections, chronic alcoholism, some chronic pulmonary diseases, autoimmune diseases, allogeneic transplantation, as well as has a great influence on age-related changes in the immune system status. CD8(+) CD28(-) (CD8(+) CD57(+)) T-cell population is heterogeneous and composed of various functionally competing (cytotoxic and immunosuppressive) subsets thus the overall effect of CD8(+) CD28(-) (CD8(+) CD57(+)) T-cell-mediated immunity depends on the predominance of a particular subset. Many articles claim that CD8(+) CD28(-) (CD8(+) CD57(+)) T cells have lost their proliferative capacity during process of replicative senescence triggered by repeated antigenic stimulation. However recent data indicate that CD8(+) CD28(-) (CD8(+) CD57(+)) T cells can transiently up-regulate telomerase activity and proliferate under certain stimulation conditions. Similarly, conflicting data is provided regarding CD8(+) CD28(-) (CD8(+) CD57(+)) T-cell sensitivity to apoptosis, finally leading to the conclusion that this T-cell population is also heterogeneous in terms of its apoptotic potential. This review provides a comprehensive approach to the CD8(+) CD28(-) (CD8(+) CD57(+)) T-cell population: we describe in detail its origins, molecular and functional characteristics, subsets, role in various diseases or conditions, associated with persistent antigenic stimulation.

Imbalance in T-cell and cytokine profiles in patients with relapsing-remitting multiple sclerosis

Multiple sclerosis (MS) is characterized by autoimmune attack leading to demyelination of the white matter in the central nervous system with devastating clinical consequences. Several immune-mediated destruction mechanisms were previously proposed including different T-cell subsets but complex view on immune system function in patients with MS is missing. In the present study, T-lymphocyte populations and pro-inflammatory as well as suppressive cytokine profiles were evaluated in detail in previously untreated patients with relapsing-remitting MS (RRMS). CD4(+) and CD8(+) naïve, central memory (Tcm), effector memory (Tem), terminal effector memory (Ttem), CD4(+) regulatory T-cells (Treg) and CD8(+) T-suppressor cells (Ts) were analysed using flow cytometry, and levels of ten plasma cytokines were determined using fluorescent bead-based immunoassay. We evaluated two groups of RRMS with minor (n=33) and major (n=25) clinical impairment and compared them with healthy controls (n=40) in order to detect any correlation between severity of MS clinical symptoms and immune disturbances. Significant differences were noted in CD4(+)CD45RA(+)CCR7(+) naïve T-cells, CD4(+)CD45RO(+)CCR7(-) and CD8(+)CD45RO(+)CCR7(-) Tem cells, while no differences were recognized in Tcm, Ttem, Treg and Ts cells in RRMS patients. Nine out of ten studied cytokines were disturbed in plasma samples of patients with RRMS. In conclusion, we demonstrate complex immune dysbalances in untreated MS patients.

Harnessing regulatory T cells for the therapy of lupus and other autoimmune diseases

Regulatory T cells (Tregs) maintain immunological homeostasis and prevent autoimmunity. The depletion or functional alteration of Tregs may lead to the development of autoimmune diseases. Tregs consist of different subpopulations of cells, of which CD4(+)CD25(+)Foxp3(+) cells are the most well characterized. However, CD8 Tregs also constitute a major cell population that has been shown to play an important role in autoimmune diseases. This review will discuss the role of Tregs in autoimmune diseases in general and specifically in systemic lupus erythematosus (SLE). SLE is a multisystem autoimmune disease characterized by the production of autoantibodies against nuclear components and by the deposition of immune complexes in the kidneys as well as in other organs. Abnormalities in Tregs were reported in SLE patients and in animal models of the disease. Current treatment of SLE is based on immunosuppressive drugs that are nonspecific and may cause adverse effects. Therefore, the development of novel, specific, side effect-free therapeutic means that will induce functional Tregs is a most desirable goal. Our group and others have designed and utilized tolerogenic peptides that ameliorate SLE manifestations in murine models. Here, we demonstrate the role of CD4 and CD8 Tregs, as well as the interaction between the two subsets of cells and the mechanism of action of the tolerogenic peptides. We also discuss their therapeutic potential for the treatment of SLE.

Identification of small-molecule inhibitors against human leukocyte antigen-death receptor 4 (HLA-DR4) through a comprehensive strategy

Rheumatoid arthritis (RA) is an autoimmune disease mediated by T-lymphocytes and associated with the human leukocyte antigen-death receptor 4 (HLA-DR4). The HLA-DR4 protein selectively interacts with the antigenic peptides on the cell surface and presents them to the T cell receptor (TCR) on CD4+ T cells. The HLA-DR4-antigen-TCR complex initiates the autoimmune response and eventually causes the chronic inflammation within patients bodies. To inhibit HLA-DR4-restricted T cell activation, an ideal approach is to discover non-T cell stimulating substrates that specifically bind to HLA-DR4. In this paper, a comprehensive structure-based design strategy involved de novo design approach, pharmacophore search, and dock method was presented and applied to "simplify" the known binding peptide ligand of HLA-DR4 and identified specific small-molecule inhibitors for HLA-DR4. The designed three-step strategy successfully identified five nonpeptide ligands with novel scaffolds from a chemical library containing 4 × 10(6) commercially available compounds within a tolerable computing time. The identified five chemicals, BAS-0219606, T0506-2494, 6436645, 3S-71981, and KM 11073, are all non-T cell stimulators and are able to significantly inhibit HLA-DR4-restricted T cell activation induced by type II collagen (CII) 263-272 peptide. IC(50) for the best two potentials, BAS-0219606 and T0506-2494, was 31 and 17 μM, respectively, which is equivalent or better than the known peptide ligands. It is hopeful that they can be used as effective therapeutic means for further treatment of RA patients. In addition, the comprehensive strategy presented in this paper exhibited itself to be an effective flow line from peptide ligands to small-molecule inhibitors and will have applications to other targets.

CD8+CD122+ regulatory T cells (Tregs) and CD4+ Tregs cooperatively prevent and cure CD4+ cell-induced colitis

We identified CD8(+)CD122(+) regulatory T cells (Tregs) and demonstrated their importance in the maintenance of immune homeostasis and in the recovery from experimental autoimmune encephalomyelitis. In this paper, we show that CD8(+)CD122(+) Tregs effectively prevent and cure colitis in a mouse model. In our experiments, colitis was induced in lymphocyte-deficient RAG-2(-/-) mice by transferring CD4(+)CD45RB(high) cells that were excluded with CD4(+) Tregs. Cotransfer of CD8(+)CD122(+) cells clearly suppressed the development of colitis, and this suppressive effect was similar to that of CD4(+)CD45RB(low) cells that were mostly CD4(+) Tregs. CD8(+)CD122(+) cells obtained from IL-10(-/-) mice were unable to suppress colitis, indicating that IL-10 is an important effect-transmitting factor in the suppression of colitis. CD8(+)CD122(+) cells showed a suppressive effect when they were transferred 4 wk after CD4(+)CD45RB(high) cells, indicating the therapeutic potential of CD8(+)CD122(+) cells. A mixture of CD8(+)CD122(+) cells and CD4(+)CD45RB(low) cells was far more effective than single Tregs, indicating the synergistic effect of these Tregs. These overall findings demonstrate the potential role of CD8(+) Tregs, and possibly together with CD4(+) Tregs, in the medical care of inflammatory bowel disease patients.

CD8(+) T regulatory/suppressor cells and their relationships with autoreactivity and autoimmunity

Regulatory T lymphocytes (Treg) are fundamental for immune homeostasis since they contribute to the induction of peripheral tolerance to autologous antigens and regulate effector immune responses. Treg subsets are present within both the CD4+and the CD8(+) T cell compartments. Considering the CD8(+) Treg, in the last decades several subpopulations, provided with different phenotypes and mechanisms of action, have been characterized. This review is an attempt of integrating in an organic scenario the different CD8(+) Treg subpopulations. Moreover, it summarizes the findings so far achieved on the existence of CD8(+) Treg alterations in autoimmune diseases.

Research advancement in immunopathogenesis of myasthenia gravis

Myasthenia gravis (MG) is an autoimmune neuromuscular junction disease mediated by antibodies against the acetylcholine receptor (AChR). The etiology and immunopathogenesis of MG remain unclear. Recent research has shown the involvement of autoantibodies, lymphocytes, cytokines and chemokines, in the pathogenesis of MG. Systematic factors are also demonstrated, such as inheritance and endocrine. This review indicates the research development in immunopathogenesis of MG.

CD8+ Tregs in lupus, autoimmunity, and beyond

While CD4(+)CD25(high) regulatory T cells (Tregs) have garnered much attention for their role in the maintenance of immune homeostasis, recent findings have shown that subsets of CD8(+) T cells (CD8(+) Tregs) display immunoregulatory functions as well. Both CD4(+) Tregs and CD8(+) Tregs appear impaired in number and/or function in several autoimmune diseases and in experimental animal models of autoimmunity, suggesting the possibility of immunotherapeutic targeting of these cells for improved management of autoimmune conditions. Our group has developed a strategy to induce CD8(+) Tregs in autoimmune mice through the use of a tolerogenic self-peptide, and new information has been gained on the phenotype, function and role of induced CD8(+) Tregs in autoimmunity. Here we present an overview of the role and mechanisms of action of CD8(+) Tregs in autoimmunity, with a special focus on lupus. We also discuss the potential role of CD8(+) Tregs in other diseases, including chronic infection and cancer.

Numerical defects in CD8+CD28- T-suppressor lymphocyte population in patients with type 1 diabetes mellitus and multiple sclerosis

Type 1 diabetes mellitus (T1D) and multiple sclerosis (MS) are organ-specific autoimmune diseases leading to an attack of auto-aggressive lymphocytes against the pancreatic beta-cells and central nervous system, respectively. Using four-colour flow cytometry, T-lymphocyte populations having an important function in autoimmune processes were analyzed. T-regulatory cells (Treg) CD4(+)CD25(+)CD127(low), T-suppressor cells (Ts) CD8(+)CD28(-), activated helper CD4(+)CD25(+)CD127(+) and cytotoxic CD8(+)CD25(+) T-cells and also naive CD4(+)CD45RA(+) and memory T-cells CD4(+)CD45RO(+) were compared in the group of patients with T1D (n=30), MS (n=31) and in the group of healthy controls (n=29). Significant differences in Ts cells, activated helper and cytotoxic cells and also memory T-cells were recognized in the group of T1D patients compared to healthy controls. Ts population was significantly lowered in MS patients as well. However, no significant differences were noticed in Treg population. The observed data demonstrate significant differences among patients with T1D and MS in comparison to healthy individuals.

IL-6 positively regulates Foxp3+CD8+ T cells in vivo

Although recent studies have identified regulatory roles for Foxp3(+)CD8(+) T cells, the mechanisms that induce their development and underlie their functions in vivo have not been elucidated. Here, we show that IL-6 positively regulates the Foxp3(+)CD8(+) T-cell development and function. The Foxp3(+)CD8(+) T cells that differentiated in vitro in the presence of IL-6 suppressed autoimmune colitis and arthritis in vivo. Moreover, Foxp3(+)CD8(+) T cells that developed in vivo in the presence of enhanced IL-6 signaling suppressed the development of a spontaneous T(h)17 cell-mediated autoimmune arthritis. Thus, we concluded that Foxp3(+)CD8(+) T cells develop in response to IL-6 and regulate chronic inflammation in T(h)17 cell-mediated F759 autoimmune arthritis. These results suggested that Foxp3(+)CD8(+) T cells may develop in response to IL-6 under certain inflammatory conditions in vivo and may regulate some other chronic inflammation diseases.

DC-induced CD8(+) T-cell response is inhibited by MHC class II-dependent DX5(+)CD4(+) Treg

CD4(+) T cells are important for CD8(+) T-cell priming by providing cognate signals for DC maturation. We analyzed the capacity of CD4(+) T cells to influence CD8(+) T-cell responses induced by activated DC. Surprisingly, mice depleted for CD4(+) cells were able to generate stronger antigen-specific CD8(+) T-cell responses after DC vaccination than non-depleted mice. The same observation was made when mice were vaccinated with MHC class II(-/-) DC, indicating the presence of a MHC class II-dependent CD4(+) T-cell population inhibiting CD8(+) T-cell responses. Recently we described the expansion of DX5(+)CD4(+) T cells, a T-cell population displaying immune regulatory properties, upon vaccination with DC. Intriguingly, we now observe an inverse correlation between CD8(+) T-cell induction and expansion of DX5(+)CD4(+) T cells as the latter cells did not expand after vaccination with MHC class II(-/-) DC. In vitro, DX5(+)CD4(+) T cells were able to limit proliferation, modulate cytokine production and induce Foxp3(+) expression in OVA-specific CD8(+) T cells. Together, our data show an inhibitory role of CD4(+) T cells on the induction of CD8(+) T-cell responses by activated DC and indicate the involvement of DX5(+)CD4(+), but not CD4(+)CD25(+), T cells in this process.

Systemic immune effects of adjuvant chemotherapy with 5-fluorouracil, epirubicin and cyclophosphamide and/or radiotherapy in breast cancer: a longitudinal study

Immunotherapy is being increasingly utilized for adjuvant treatment for breast cancer (BC). We have previously described immune functions during primary therapy for BC. The present study describes immune recovery patterns during long-term, unmaintained follow-up after completion of adjuvant therapy.A group of patients with primary BC had been treated with adjuvant radio-chemotherapy (RT + CT) 5-fluorouracil, epirubicin and cyclophosphamide (FEC) (n = 21) and another group with radiotherapy (RT) (n = 20) alone. Immunological testing of NK and T-cell functions was performed initially at the end of adjuvant treatment and repeated after 2, 6 and 12 months. NK cell cytotoxicity was significantly higher (P < 0.05) at all time-points in patients than in age-matched controls and did not differ between the two treatments groups during one year observation. In contrast, lower numbers of CD4 T-cells and lower expression of CD28 on T-cells was observed particularly in RT + CT patients and did not normalize during the observation period. The numbers of T(reg) cells (CD4(+)CD25(high)) were low in the RT + CT group during follow-up, as well as expression of TCRxi, Zap70, p56(lck), P59(fyn) and PI3 k in CD4(+) cells. In contrast, expression of intracellular cytokines (IFN-gamma, IL-2, IL-4) in CD4 and CD8 T cells were significantly higher in RT + CT patients than in the RT group and the difference increased during follow-up. In conclusion, NK-cell cytotoxicity increased during unmaintained long-term follow-up whereas CD4 and regulatory T cells as well as signal transduction molecules remained low following adjuvant radio-chemotherapy.

Induction of immune tolerance by activation of CD8+ T suppressor/regulatory cells in lupus-prone mice

Multiple CD8(+) suppressive T cell (Ts) subtypes are now recognized as essential regulators of the immune system that prevent autoimmunity through secretion of multiple cytokines and the subsequent inhibition of effector lymphocyte function. CD8(+) Ts are an exciting area of study because of the possible therapeutic implications of inducing suppressive cells that are able to subdue or anergize autoimmune manifestations. Current research in systemic lupus erythematosus (SLE), a disease in which most effective therapies are widely immunosuppressive, is often focused on novel and highly targeted ways in which to treat this multiorgan disease. CD8(+) Ts have been impaired in human and murine SLE. Our group and others have utilized tolerogenic peptides to induce and study CD8(+) Ts to understand their function, as well as investigate a possible new SLE therapy. This review will discuss the similarities and differences in CD8(+) Ts subsets, the concept of tolerance as a therapy, and the current understanding of CD8(+) Ts in mouse SLE models.

Inhibitory CD8+ T cells in autoimmune disease

Rheumatologists have long been focused on developing novel immunotherapeutic agents to manage such prototypic autoimmune diseases as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). The ultimate challenge in providing immunosuppressive treatment for patients with RA and SLE has derived from the dilemma that both protective and harmful immune responses result from adaptive immune responses, mediated by highly diverse, antigen-specific T and B cells endowed with powerful effector functions and the ability for long-lasting memory. As regulatory/suppressor T cells can suppress immunity against any antigen, including self-antigens, they emerge as an ideal therapeutic target. Several distinct subtypes of CD8(+) suppressor cells (Ts) have been described that could find application in treating RA or SLE. In a xenograft model of human synovium, CD8(+)CD28(-)CD56(+) T cells effectively suppressed rheumatoid inflammation. Underlying mechanisms involve conditioning of antigen presenting cells (APC). Adoptively transferred CD8(+) T cells characterized by IL-16 secretion have also exhibited disease-inhibitory effects. In mice with polyarthritis, CD8(+) Ts suppressed inflammation by IFNgamma-mediated modulation of the tryptophan metabolism in APC. In SLE animal models, CD8(+) Ts induced by a synthetic peptide exerted suppressive activity mainly via the TGFbeta-Foxp3-PD1 pathway. CD8(+) Ts induced by histone peptides were found to downregulate disease activity by secreting TGFbeta. In essence, disease-specific approaches may be necessary to identify CD8(+) Ts optimally suited to treat immune dysfunctions in different autoimmune syndromes.